The embodiments described herein relate generally to an electric machine, and more specifically, to attaching power to stator coils associated with the electric machine.
An electric machine is typically in the form of an electric generator or an electric motor. The machine typically has a centrally located shaft that rotates relative to the machine. Electrical energy applied to coils within the motor initiates this relative motion which transfers the power to the shaft and, alternatively, mechanical energy from the relative motion of the generator excites electrical energy into the coils. For expediency the machine will be described hereinafter as a motor. It should be appreciated that a motor may operate as a generator and vice versa.
A stationary assembly, also referred to as a stator, includes a stator core and coils or windings positioned around portions of the stator core. It is these coils to which energy is applied to initiate this relative motion which transfers the power to the shaft. These coils are formed by winding wire, typically copper, aluminum or a combination thereof, about a central core to form the winding or coil.
In an assembled configuration the coils are positioned in a spaced apart relationship about the stationary assembly that typically has a generally hollow cylindrical configuration with the coils positioned internally. The power of the electric motor is dependent on the amount of energy that may be applied to the coils and that amount of energy is proportional to the amount of wire that may be positioned about the stationary assembly. The amount of wire positioned about the stationary assembly is typically referred to as the slot fill. Placing as much wire in the coils as possible, also known as maximizing the slot fill is thus desirable.
Of many methods of manufacturing the stator and winding the wire to form the coil in particular, the following three methods are typical. The first is to form a rigid hollow cylindrical core with internal protrusions of teeth around which the coils are wound. The core is typically produced by stacking a plurality of rigid hollow laminations and joining them to form the rigid hollow cylindrical core. This method requires the wire to be fed around the teeth with a device called a needle. The need to provide for movement of the needle around the teeth limits the amount of wire that may be used to form the coil.
A second method is to similarly form a rigid hollow cylindrical core with internal protrusions of teeth and to provide spools or bobbins that may be removably secured to the teeth of the core. The coils are formed by winding wire around the bobbins while separated from the stator and then by assembling the wound bobbins onto the teeth of the stator. The separated coils provide improved access around the coil to more completely form the coil.
A third known method of manufacturing a stationary assembly includes stacking a plurality of laminations and rolling the stack to form a round stator. The laminations are stamped from a sheet of stock material and stacked to form a substantially linear array of stator sections and connecting members. The substantially linear array includes a first end and a second end. Teeth are formed along one side of the linear array. Windings may be wound on the stator sections around the teeth while the laminations are in the linear orientation in a configuration where the linear array of laminations are arched with the teeth positioned outwardly. Once the windings are positioned on the stator sections, the stack is formed into a second shape. To form the stack into the second shape, the stack is rolled around a central axis and the first end is coupled to the second end with the teeth positioned inwardly. The second shape is the substantially round shape of a stator. Typically, the second shape is maintained by securing the first end to the second end. The linear arrays provide improved access around the teeth to more completely form the coil.
As described above, it is these stator coils to which energy is applied to transform the stator coils into electro magnets that attract portions of the rotor to initiate relative motion between the rotor and the stator which transfers the power to the shaft. In order for the rotor to rotate in a particular direction the application of power to the various stator coils to transform them into electromagnets needs to occur in proper order so the energized coils cooperate with their corresponding rotor portion, called a rotor pole, to urge the rotor in that particular direction.
The selecting of energized coils can be varied such that the same physical motor may operate with a various power sources, including for example voltages of 12 Volts to 575 Volts, and in particular a 110 Volt power source, 220 Volt power source, or 440 Volt power source. Likewise the same physical motor may operate with a single phase power source or a three phase power source. Such selecting of energized coils may be determined by electrical wires that connect electrical power to the individual stators coils. These wires are typically coated or shielded with electrical insulation and are commonly called lead wires.
Thus the same physical motor (a motor with the same stator and the same rotor may operate with a 42 Volt power source, 220 Volt power source, or 440 Volt power source or a single phase power source or a three phase power source by merely changing the arrangement of the lead wires and magnet wires that connect electrical power to the individual stators coils. For low voltage operation (110 volt) the magnet wires may be the same coated wire as those used as magnet wire that is used to form the stator coils, but for higher voltage operation (440 volt) the lead wires are more heavily insulated than the coated wires used in the stator coil. The changing of the arrangement of the lead wires and magnet wires that connect electrical power to the individual stators coils may create one of several widely used electrical wiring configurations for motors that assist in providing for the use of the same physical motor for use with a single phase power source or a three phase power source or for low voltage operation or for higher voltage operation. Three of these widely used electrical wiring configurations for motors are commonly known as series, series parallel and parallel connections.
To minimize undesired electrical field and undesired magnetic interaction of the lead wires and the stator coils and to minimize power loss and lead wire cost, the lead wires are preferably precisely positioned on an and of the stator coils. The positioning of these wires requires skilled manual assembly or extremely complicated automation. Further the interior of motors, particularly those under high loads and extreme environments may have high temperature and particularly high temperatures at the coils. Since the rotor is rotating during operation at high speeds and since the motor and/or the environment may have unbalanced forces creating vibrations, having these wires properly secured in the their precise position may be very important.
For low voltage operation (110 volt) the lead wires may be the same coated wire that is used to form the stator coils, but for higher voltage operation (440 volt) the lead wires are more heavily insulated than the coated wires or magnet wire used in the stator coil. The connection of these lead wires to the coil wires needs to be secure to accommodate the environment of the motor as described above and the connections should preferably be easily performed to minimize labor and reduce chances of improper assembly. The present invention is directed to alleviate at least some of these problems with the prior art.